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https://issues.apache.org/jira/browse/DERBY-269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12613458#action_12613458
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Mamta A. Satoor commented on DERBY-269:
---------------------------------------
I spent time looking through selectivity.sql and tried converting the test
cases into just a sql file where we do not rely on the old functionality which
is not supported anymore. The existing selectivity.sql depends on the features
like Object.methods eg runtimestatistics().rts.getEstimatedRowCount(),
runtimestatistics().getScanStatisticsText('TEMPLATE') inside of sql.
eg
create view showstats as
select cast (conglomeratename as varchar(20)) indexname,
cast (statistics.toString() as varchar(40)) stats,
creationtimestamp createtime,
colcount ncols
from sys.sysstatistics, sys.sysconglomerates
where conglomerateid = referenceid;
Such object lookup is not available in Derby. I will spend more time on it but
it may not work out with the curent Derby functionality.
I was wondering if community had any ideas/test cases which I can use for the
new stored procedure. I can do basic testing which shows that the stored
procedure runs etc but it will be nice to see the real impact of running the
stored procedure on a query before and after the update statistics runs. Thanks
for any help with this.
> Provide some way to update index cardinality statistics (e.g. reimplement
> update statistics)
> --------------------------------------------------------------------------------------------
>
> Key: DERBY-269
> URL: https://issues.apache.org/jira/browse/DERBY-269
> Project: Derby
> Issue Type: New Feature
> Components: SQL
> Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.2.2.0, 10.3.1.4
> Reporter: Stan Bradbury
> Assignee: Mamta A. Satoor
> Attachments: DERBY269_update_statistics_svndiff_ver1.txt,
> DERBY269_update_statistics_svnstat_ver1.txt
>
>
> Performance problems are being reported that can be resolved by updating the
> cardinality statistics used by the optimizer. Currently the only time the
> statistics are guaranteed to be an up-to-date is when the index is first
> created on a fully populated table. This is most easily accomplished on an
> existing table by using the command:
> alter table <table-name> compress [sequential]
> Compress table is an I/O intensive task. A better way to achieve this would
> be to re-enable parser support for the 'update statistics' command or
> re-implement the update in some other fashion.
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